The present invention pertains to the sector of typography and lithography machines, and it specifically pertains to machines for the creasing, perforation or circular cutting of paper or the like, in sheets of any basic weight.
Essentially manual, press creasing machines, in which the creasing is obtained by means of pressing the paper in the form of sheets between two complementarily shaped plates, are known in the current state of the art. However, the use and the productive capacity of these machines are very limited because of their intermittent action as well.
Creasing machines are also known, in which the starting sheets of paper are guided between rotating creasing tools. However, these machines also have various drawbacks and disadvantages. In them, the feeding of the paper is carried out with an especially complex and cumbersome rotary system or by means of a paper-holding plane that is progressively moved upwards and that, as such, does not ensure the maximum efficiency, velocity and continuity of feed of the sheets. Moreover, the rotating creasing or perforation means adopted and used up to now are not suitable for all types of paper and even less so for digitally printed paper. These means are generally rigid and tend to make cuts in and crumble the printed layer in the presence of digitally printed paper, altering the quality thereof along and on the edges of the creasing or perforation that will be carried out.
The present invention is aimed at finding a solution for the drawbacks and limitations of the prior-art creasing, perforation or cutting machines and correspondingly at proposing a creasing or a perforating machine that makes possible more efficient feeding of the paper as well as the creasing, perforation or cutting process on any type of paper, of any basic weight as well as of paper coming from a preventive digital printing.
To this end the present invention proposes a machine for the creasing, perforation or circular cutting of sheets of paper, which is improved in terms of the system for feeding the starting sheets, the means for advancing each sheet, and the creasing or perforating unit.
The feeding system has a fixed-height plane, and it can accommodate a stack of sheets for prolonged autonomy of operation of the machine. Each sheet is taken from the bottom of the stack of sheets and is advanced to the creasing or perforating unit. The sheet is carried long by movable belts and with the aid of a suction roller. The creasing unit comprises circular tools having a compound structure so as not to have an effect on the printing of the sheets even if this printing is of the digital type and regardless of the basic weight of the paper.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.